Conveyors of articles, and in particular belt, carpet, or chain conveyors, are used in many industrial or civilian fields, from food industry to airports. In very general terms, a conveyor comprises one or more transport elements, adapted to provide a support surface for the products to be transported, which are made to advance along a conveying path by suitable moving means such as electric motors, pinions and driving gears. In particular, carpet or belt conveyors use as transport means a chain consisting of several segments formed by a plurality of links, hinged together by means of respective pins to form a support surface substantially flat, smooth, destined to the support of the articles to by carried.
Like all mechanical systems, also transporters and their components are subject to wear during their operation. For example, the pins that hinge the links of the chain segments may wear off when subjected to prolonged efforts. In plastic chains with steel pin, the seat of the pin wears more than the pin itself, while in chains entirely made of steel or entirely made of plastic, wear is present in similar proportions both on the pin and on the hinge seat of the pin. In any case, due to wear, the links that make up the chain segments may tend to open up and move away one from the other, with the result that the surface of the transport element no longer provides the necessary carrying capacity. The separation of the links caused by wear causes a consequent progressive elongation of the chain, which, if excessive, may adversely affect the correct coupling of the chain with the pinions. Indeed, when the elongation becomes excessive, the chain links, at the time of coupling with the teeth of the pinion, tend to move to the tip of the teeth rather than near the bottom of the space between two successive teeth.
The progressive separation of the chain links from the bottom of the space between successive teeth of the pinion is such as to cause a gradual variation of the chain movement speed. If the elongation of the chain due to the opening of the links exceed a certain critical threshold, such as for example 3% of the initial length, the chain may skip a tooth of the pinion, causing the chain to be subjected to very high dynamic stresses, and therefore determining more or less frequent halts in the flow of transported articles, and consequent falls of the same from the transport chain.
For this reason, the conveyors require periodic inspections by qualified operators in order to control the actual amount of elongation of the chain and, where necessary, proceed to plan the plant stoppage and the repair or replacement of the chain. However, given the considerable costs associated with the traditional monitoring, it is preferable to implement a system capable of automatically monitoring the elongation of the chains of the conveyor. For example, each chain may be provided with a proper smart measuring device capable of measuring the elongation of the chain and to report in real time when such elongation has exceeded a predetermined critical threshold. However, implementing an automatic monitoring system of this type proves to be very complex, for the following reasons.
First, since the effective size to be detected is a relatively small quantity (the critical threshold is of the order of 3%), the measuring device should be sufficiently precise. Moreover, the majority of the measuring devices of this type currently widespread in the market are very complex, as adapted to detect the magnitude (elongation) by means of a local measurement. Then, taking into account the fact that in a single site (for example, a factory) there may be a large number of conveyors, each comprising a plurality of chains, and that each chain may be subject to elongation independently from the others, the number of measuring devices of the automatic monitoring system may easily rise until reaching a high value. Finally, the measuring devices must necessarily be robust in order to correctly operate even in the adverse conditions that may occur in a hostile work environment like an industrial plant, such as for example the presence of electrical machinery in the vicinity of the conveyors that may generate not negligible electromagnetic interference, high temperatures, excessive humidity, presence of dust, vibrations, and aggressive cleaning chemicals.